This invention relates to a dispensing unit for liquid, of the type comprising a liquid filled container in which is mounted a finger operated pump having a plunger which ejects a spray of liquid when it is depressed.
In packaging liquids which are to be dispensed by being sprayed in measured amounts, it is common to utilize a liquid filler container provided with a pump having a plunger or stem which releases a jet of liquid when the plunger or stem is depressed. Liquids packaged in such a manner may, for example, include various types of household cleaning liquids, perfumes, oral sprays and the like.
One type of prior dispensing unit includes a pump body extending vertically within a liquid filled, sealed container having a low pressure gas therein for supplying material from the container to the pump. A plunger passes through a chamber in the pump body. The lower end of the plunger or stem controls a valve at the lower end of the chamber. When the plunger or stem is in a raised position relative to the pump body the valve places the chamber in communication with the interior of the container. A piston in the chamber prevents fluid communication between an outlet passage in the upper part of the stem and the chamber beneath the piston when the stem is in the raised position. An initial downward movement of the stem causes closing of the valve at the lower end of the chamber and then moves the outlet passage downwardly of the piston into fluid communication with the chamber below the piston. Continued downward motion moves the piston downwardly expelling the liquid in the upper chamber via the outlet passage. On subsequent return motion of the plunger or stem, the piston travels upwardly creating a region of suction in the chamber until the plunger is elevated sufficiently to open the valve at the lower end of the chamber so that liquid flows in from the interior of the container under the force of the low pressure gas. Such a pump is disclosed, for example, in applicant's prior U.S. Pat. No. 3,211,346. A pump which works similarly, except that during the up stroke, the valve at the lower end of the chamber is opened simultaneously with the opening of the outlet passage, is disclosed in Corsette U.S. Pat. No. 3,237,571. See also, Gorman U.S. Pat. No. 3,187,960.
Additional venting structure may be provided in a pump of this general type to admit air to the interior of the container to replace the liquid expelled so that a partial vacuum is not developed within the container which would prevent flow of liquid into the chamber. Pumps having a general venting structure are disclosed, for example, in O'Donnell et al. U.S. Pat. No. 3,159,316; Fedit U.S. Pat. No. 3,331,559 and Boris U.S. Pat. Nos. 3,239,151 and 3,627,206.
In a different type of unit, a refillable aerosol valve rather than a finger operated pump of the present invention, it has been known to utilize a construction as shown in O'Donnell U.S. Pat. No. 3,473,704.
In each of these prior art patents (other than my U.S. Pat. No. 3,211,346) the valve at the lower end of the chamber is always opened as soon as the piston begins to move upward. That is to say, in general, check valves are used, most typically a ball check valve. Although this type of valve works well, it does have some problems in that they are subject to improper seating if the dispenser is not held properly and add to the cost of manufacture of the valve.
In dispensing units using pumps, there are a number of basic requirements. Because these pumps are usually thrown away after use, the cost of the pump must be kept as low as possible. Ideally, if the pump parts can all be made of molded plastic in such a way that they are easily assembled, this requirement will be met. Furthermore, particularly when being used for dispensing liquid such as perfumes, which are highly volatile, a good seal sealing of the venting passages is needed. Finally, the pump must operate reliably to dispense the measured amount of the liquid with each stroke. None of the prior art devices meet all these requirements. Thus, it becomes evident that there is a need for an improved pump which will provide all the above noted features.